Open cooling system question

I have found a blocked cooling system tube on my 03 GTX DI. In the cooling diagram below the block is located in tube number 1 and is located towards the jet pump. It is stuffed full of sand, about 30cm back from the pump.

Which way does the water flow trough this pipe? I am going to try and pull the pipe off at the engine side and try and flush it out towards the back. But I am not sure if I will be able to get it due to its location

Can anyone tell me the direction of water flow? Where is the primary water intake?